1. Brief Description of the Invention
The present invention concerns cleaning compositions which surprisingly exhibit greater cleaning performance when a solubilizing coupler concentration is increased beyond that necessary to completely solubilize an organic solvent. A method of cleaning hard surfaces using the compositions of the invention is also described.
2. Related Art
Chemical cleaners are a significant portion of the industrial cleaning market. A chemical cleaner is typically aqueous and comprises an organic solvent to solubilize various soils, a surfactant which serves as a wetting agent, and a builder which serves to chelate ions present in water, such as magnesium and calcium. The types and ratios of these ingredients can vary considerably depending on the types of soils to be cleaned and the performance desired. It is common that all components are water soluble. In some instances, however, particularly with the solvent ingredient, the water solubility can be negligible. In these cases, components commonly called "couplers" or "hydrotropes" are used to increase the apparent water solubility of the organic solvent in the cleaning composition. The amount of coupler required depends on the type of coupler, organic solvent, and the other components of the mixture.
It is typically preferred to use the minimum amount of coupler necessary to completely solubilize the solvent, as this tends to reduce the cost of the cleaning composition. Further, as noted in U.S. Pat. Nos. 5,080,822 and 5,080,831, in conventional compositions as the amount of coupler increases, the cleaning performance typically decreases.